Welcome to Coastal Landscapes!
Welcome to one of the most dynamic parts of your Geography A Level. We are diving into Coastal Landscapes, which is part of your Physical Systems unit. Think of the coast not just as a place for a holiday, but as a giant, never-ending battleground between the land and the sea. You will learn how the coast works like a machine (a system), how incredible shapes like arches and spits are built, and how humans and climate change are constantly rewriting the script. Don't worry if it seems like a lot of terminology at first—we will break it down bit by bit!
1. Coastal Landscapes as Systems
To understand a coast, geographers view it as a system. Imagine a factory: you have things coming in (raw materials), things happening inside (the work), and things coming out (the finished product).
The System Components
- Inputs: These are things that "enter" the system. Examples include kinetic energy from wind and waves, thermal energy from the sun, and material like sediment from cliffs or rivers.
- Processes: This is the "work" being done. It includes erosion (wearing away), transportation (moving stuff), and deposition (dropping stuff).
- Outputs: These are things that "leave" the system, such as sediment being moved far out to sea or coastal land being lost to the ocean.
The Sediment Cell
A sediment cell is a distinct area of the coastline (usually between two headlands) where the movement of sand and shingle is mostly self-contained.
Analogy: Think of a sediment cell like a closed bank account. You can move money (sand) around inside the account, but it’s hard for money to get in or out from other accounts.
Quick Review: The coast is a system of inputs, processes, and outputs. A sediment cell is a "closed" loop of moving material.
2. Physical Factors Influencing the Coast
Why do some coasts have massive cliffs while others have flat beaches? It depends on these physical factors:
Winds and Waves
Wind is the primary "engine" of the coast. The speed, direction, and frequency of wind determine how powerful waves will be. The fetch is the distance of open water over which the wind blows—the longer the fetch, the bigger the wave!
Waves: The Two Types
1. Constructive Waves: These "build" beaches. They are low, long, and have a strong swash (water moving up the beach) and a weak backwash (water pulling back).
2. Destructive Waves: These "destroy" beaches. They are high, steep, and have a weak swash but a very strong backwash that sucks pebbles and sand away.
Geology (Rocks!)
This is split into two parts:
- Lithology: The physical characteristics of the rock. Is it hard (Granite) or soft (Clay)? Is it porous (lets water in)?
- Structure: How the rock is arranged. Concordant coasts have rock layers running parallel to the sea (creating coves), while Discordant coasts have rock layers at right angles to the sea (creating headlands and bays).
Did you know? The global pattern of ocean currents acts like a giant conveyor belt, moving heat and sediment across the planet, which affects how much energy a coastline has!
Key Takeaway: Wind creates waves; geology determines how the land resists those waves.
3. Where does the sediment come from?
Sediment (sand, mud, and pebbles) doesn't just appear. It comes from three main sources:
- Terrestrial (Land): Rivers bring sediment down to the sea (fluvial deposition). Cliffs also crumble due to weathering and mass movement (like landslides).
- Offshore: Waves and tides can "push" sand from the sea floor up onto the land.
- Human: We sometimes add sand to beaches to stop them from disappearing—this is called beach nourishment.
4. Shaping the Land: Erosional Landforms
When high-energy waves hit the coast, they use various geomorphic processes to wear the land away.
How Rocks are Broken Down
- Hydraulic Action: Air is trapped in cracks by a wave, compressed, and then expands violently, blasting the rock apart.
- Abrasion (Corrasion): Waves hurl pebbles against the cliff like sandpaper.
- Attrition: Rocks in the sea knock against each other and become smaller and smoother.
- Solution (Corrosion): Weak acids in seawater dissolve certain rocks like limestone.
The Sequence of Erosion
Rocks usually erode in a specific order. Mnemonic: C-A-S-S (Cave, Arch, Stack, Stump).
- Waves find a fault in a headland and create a Cave.
- Erosion goes all the way through to create an Arch.
- The roof of the arch becomes too heavy and collapses, leaving a tall pillar called a Stack.
- The base of the stack is eroded until it falls, leaving a Stump.
Quick Review: Erosion creates dramatic features like cliffs and stacks. Remember: Hydraulic Action = "Air Pressure Blast."
5. Building Up: Depositional Landforms
When the sea loses energy, it drops its load. This is deposition.
Key Landforms
- Beaches: Formed when swash is stronger than backwash.
- Spits: Long ridges of sand attached to the land at one end. They form where the coastline changes direction, but longshore drift keeps moving sediment in the original direction.
- Tombolos: A spit that grows so long it connects the mainland to an island.
- Salt Marshes: Sheltered areas behind spits where silt and mud accumulate and plants begin to grow.
Step-by-Step: Spit Formation
1. Longshore drift moves sediment along the coast.
2. The coastline turns (e.g., an estuary).
3. The sediment is dropped in the "quiet" water, building out into the sea.
4. Wind can curve the end of the spit (a "hooked" end).
Key Takeaway: Deposition happens when waves slow down. Spits and bars are the result of sediment being "pushed" along the coast.
6. Changing Sea Levels and the Landscape
Sea levels don't stay the same. They change because of climate change (heating or cooling).
Emergent Landscapes (Sea Level Falls)
When the climate cools, water is frozen into ice caps, and the sea level drops. This reveals "new" land.
- Raised Beaches: Former beaches now high above the current sea level.
- Abandoned Cliffs: Old cliffs that are no longer hit by waves.
Submergent Landscapes (Sea Level Rises)
When the climate warms, ice melts, and the sea level rises, "drowning" the land.
- Rias: Drowned river valleys (wide and shallow).
- Fjords: Drowned glacial valleys (very deep and U-shaped).
Common Mistake: Don't confuse Eustatic (sea level change) with Isostatic (land level change).
Memory Aid: Eustatic = Everywhere (the whole ocean rises). Isostatic = Island (just the local land moving up or down).
7. Human Activity and the Coast
Humans change the coast in two ways: Intentionally (Management) and Unintentionally (Economic use).
Intentional Change: Management
We build groynes (fences on the beach) or sea walls. This affects the sediment budget.
Example: If you build a groyne, you trap sand in one place, but the beach "down-drift" might starve of sand and erode faster!
Unintentional Change: Economic Development
Building ports or tourist resorts can disrupt the natural flow of the coast. For example, dredging a harbor to let ships in can remove sand that would naturally have protected the nearby cliffs.
Quick Review: Humans try to protect the coast (management) but often cause "knock-on" effects elsewhere by messing with the sediment cell.
Final Study Tip!
When you write your exam answers, always try to use the Systems Approach. Instead of just saying "the cliff eroded," say "the input of wave energy caused the process of hydraulic action, leading to the output of sediment." This shows the examiner you are thinking like a real A Level Geographer! You’ve got this!